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Notes: To avoid the trial-and-error methodology involved in developing multidrug treatments, the authors designed and tested a platform for high-throughput combination screening to easily discover pairs of small molecules that could then be explored further. Cell lines tested were dispensed at 1,000 cells per well in 5µl of medium into a 1,536-well plate either directly to compound matrix plates or adding 23nl of bortezomib and library compounds to the cells. After a 48-hour incubation, 3µl of CellTiter-Glo® Luminescent Cell Viability Assay reagent was dispensed and luminscence read to assess cell proliferation. (4209)

Notes: This article describes how a miniaturized high-throughput biochemical assay for Yes1 kinase was developed and used for screening inhibitors in small molecule libraries. Kinase activity of Yes1 was assessed by dispensing 2µl of Yes1 enzyme in a 1,536-well white multiwell plate and mixing with compounds and substrate for a total kinase reaction volume of 25µl. The amount of ADP was quantitated using the ADP-Glo™ Kinase Assay and normalized to vehicle and minus-enzyme controls. Some of the inhibitors identified in the in vitro assay were tested in a cell-based assay. Two rhabdomyosarcoma cell lines, RD and RH30, were seeded at 4,000 cells/well in a 96-well plate with 100µl of culture medium. After an overnight incubation, 100µl of medium with 0, 0.1, 1, 5, 10, 15 or 20μM of inhibitor (final concentration) was added. After 48 hours, the number of cells was assessed using the CellTiter-Glo® Luminescent Cell Viability Assay. (4354)

Notes: The authors of this paper describe the development of a high-throughput assay to screen for antibody inhbitors of 5´-ectonucleotidase activity (converts AMP to adeonsine plus free phosphate). They used the CellTiter-Glo® Cell Viability Assay to screen for activity. The CellTiter-Glo® luciferase reaction is inhibited by AMP; activity of 5´-ectonucleotidase eliminates AMP, thereby relieving the reaction from inhibition, producing light. The authors demonstrate release of the luciferase reaction from inhibition as a result of 5´-ectonucleotidase activity, and that they were able to show inhibition of 5´-ectonucleotidase activity by anti-5´-ectonucleotidase antibodies. (4261)

Notes: The authors of this study investigated the energetic effects of direct fed microbials on 1-day-old broiler chicks. They looked at body weight, feed consumption, whole-body energy expenditure, organ mass, tissue respiration rates and peripheral blood mononuclear cell (PBMC) ATP levels to explore effects on energy metabolism in control-diet chicks versus chicks receiving direct fed microbials. An ATP assay was used because previous attempts to monitor O2 use by PMBCs were inconclusive. PBMC ATP levels were measured using the CellTiter-Glo™ Luminescent Cell Viability Assay in 96-well plates using 10 × 105 cells/well. The authors also looked for differences in ATP depletion in control and experimental chick populations by using an ATP synthase inhibitor and a proton ionophore. In this study, the authors concluded that the PMBC isolated from the direct microbial fed animals consumed more ATP/cell than the controls. (4202)

Notes: The authors used a biochemical assay using Xenopus egg extracts to monitor degradation levels of two Wnt pathway components, Axin and ß-catenin, and identify modulators of the Wnt pathway. ß-catenin and Axin were expressed in vitro as firefly and Renilla luciferase fusion proteins, respectively, using the TNT® SP6 High-Yield Protein Expression System and shown to behave in Xenopus extracts in a similar way to wildtype proteins, which were expressed as radiolabled proteins in rabbit reticulocyte lysate. Degradation of labeled proteins was monitored by SDS polyacrylamide gel electrophoresis and autoradiography, and degradation of luciferase fusion proteins was examined using the Dual-Glo® Luciferase Assay. Using the Xenopus extract-based assay, the authors screened chemical libraries to identify two modulators of the Wnt pathway, then confirmed this inhibition in HEK 293 cells by demonstrating a decrease in ß-catenin expression with increasing concentrations of the inhibitors. This decrease in ß-catenin-Fluc levels was measured using the Steady-Glo™ Luciferase Assay, and luciferase activity was normalized to cell viability, as determined using the CellTiter-Glo® Assay. (4181)

Notes: Here the authors describe development of an HTS cell viability assay protocol for use with cultured cyropreserved human primary hepatocytes. Cryopreserved hepatocytes for culturing were prepared as suspensions and dispensed at 2,000 or 4,000 cells/5µl/well in collagen I-coated 1,536-well plates. Cells were allowed to attach and then 23nl of each test compound was added in a dilution series from 2.8nM to 92µM, and cells incubated for 24 or 40 hours. Five microliters of CellTiter-Glo® Reagent was added and cells were incubated 30 minutes before reading the luminescent output. IC50 values for 12 compounds were determined; a summary of the protocol is provided in Table 1 of the paper. Cultured cryopreserved hepatocytes were assayed for function using the P450-Glo® CYP3A4 assay with the Luciferin-IPA substrate. (4182)

Notes: The authors used the CellTiter®-Glo Assay to assess the effect of HER2-Affitoxin on cell viability of gastric carcinoma NCI-N87 cells, which overexpress HER2. The HER2-Affitoxin is a fusion protein of a HER2-specific Affibody and modified Pseudomonas aeruginosa exotoxin A (PE 38). This fusion protein was designed to offer an alternative method for treating tumors that do not respond to trastuzumab or have acquired resistance to current therapies. The CellTiter-Glo® Assay was used to calculate HER2-Affitoxin IC50 values of cells in culture. They describe the mechanism of action as follows: HER2-Affitoxin binds to HER2 protein on the cell surface, is internalized, where it blocks protein synthesis in the cytosol via ADP ribosylation of eEF-2. (4131)

Notes: The authors of this study set out to describe the mechanism of cell death through which TNF-like weak inducer of apoptosis (TWEAK) exerts its apoptotic effect on certain cancer cells. The used the CellTiter-Glo® Cell Viability Assay and the the Caspase-Glo® 3/7 Assay to investigate cell viability and mechanism of cell death in HSC3 cells treated with TWEAK. They looked at caspase-8 activity in cells treated with TWEAK in the presence or absence of a caspase-8 inhibitor using the Caspase-Glo® 8 Assay. They showed that TWEAK induces caspase-dependent apoptosis in these cells. (4170)

Notes: Dysregulation of the NF-kB pathway has been associated with the formation of a wide variety of tumors and other cancers, as well as diseases, including chronic inflammation and immunodeficiency. Because of the association of constitutive NF-kB regulation and tumors, inhibition of the NF-kB pathway by small molecule antagonists was thought to be a means of reversing or halting the growth and spread of tumors.
The authors screened compounds from a database (the NCGC Pharmaceutical Collection or NPC) of small molecule compounds: 52% of the compounds have been approved for human or animal use by the FDA, 22% were drugs approved for use in Europe, and another 25% either drugs approved in other countries or compounds that have been tested in clinical trials. The database served as a source from which to rapidly and efficiently identify already approved drugs that inhibited NF-kB. They used a quantitative high-throughput screening format.
To identify small molecules that could inhibit the NF-kB pathway, the compounds were initially screened using a cell-based NF-kB lactamase reporter gene assay, with TNFalpha and MG132 as positive controls. (TNFalpha induced NF-kB coupled beta-lactamase activity, while MG132 blocked TNFalpha induction NF-kB-coupled beta-lactamase activity.) After several rounds of screening, 20 compounds were further studied for their NF-kB inhibition, with NF-kB luc2P HEK293 cells. After a concordance rate of 95% between the luciferase and beta-lactamase tests, compounds were additionally examined for their ability to affect caspase 3/7 activity, for the ability to disrupt the electrochemical gradient across the mitochondrial membrane in relation to cellular apoptosis, as well as tests of the inhibitors on cancer cell viability and affects on LDH release, an indicator of cell necrosis. (4049)

Notes: The authors investigated the role of pioglitazone on transcriptional regulation of the apoA-I gene and looked at the biological properties of pioglitazone-induced apoA-I-containing high-density lipoprotein particles (HDL). To investigate the biological properties of the HDL particles, the authors treated THP-1 cells with conditioned medium from HepG2 cultures treated or untreated with pioglitazone and looked at adhesion to human aortic endothelial cells (HAEC). During the experiment, HAEC viability and proliferation were monitored using the CellTiter-Glo® Luminescent Cell Viability Assay. Additionally, to determine whether pioglitazone stimulates apoA-I transcription, a luciferase reporter construct was made containing the apoA-I gene promoter. Transfected cells were treated with pioglitazone, and luciferase expression was monitored using the Dual-Luciferase® Reporter Assay System. (4173)

Notes: The authors of this study describe a proof-of-concept screen to use mammary epithelial cells that have been induced to undergo an epithelial to mesenchymal transition (EMT) as model cells to identify agents that may be selectively toxic against "epithelial cancer stem cells" (CSCs). They induced the transformed breast cancer cell line HMLER to undergo a mesenchymal transition using shRNA directed against the E-cadherin gene. They characterized the responsiveness of these transitioned cells to common cytotoxic agents using the CellTiter® 96 AQueous Cytoxicity Assay and compared the response to that of HMLER cells containing a control shRNA. They showed that the HMLER cells induced to undergo EMT behaved more like CSCs. The researchers then performed a proof-of-concept high-throughput screen to identify compounds that targeted the HMLER cells induced to undergo EMT, using the CellTiter-Glo® Assay to assess cell viability. (4006)

Notes: The authors review the use of in vitro cytotoxicity testing in drug discovery to characterize the toxic potential of new chemical entities (nce) at the earliest stages of profiling. DOI: 10.2174/1875397300903010033 (4000)

Notes: The authors describe a multiplexed in vitro assay to detect nephrotoxicity and gain information about mechanism of cell death in HK-2 (human kidney-2) cells. The multiplexed assay involved an LDH assay to detect necrosis, a caspase-3/7 assay to detect apoptosis, a reazurin assay to assess metabolic state, and a DNA dye staining assay to monitor nuclear morphology. (4002)

Notes: In this paper, the role of prostaglandin E2 (PGE2) stimulation of integrin-linked kinase (ILK) in human lung carcinoma was explored. Mutations of Sp1 and NF-κB cis-acting elements in an ILK promoter-pGL3-Basic Vector construct were created using the GeneEditor™ in vitro Site-Directed Mutagenesis System. The mutations were confirmed via sequencing. Human non–small cell lung carcinoma (NSCLC) cells were plated at a density of 5 × 105 cells per well in six-well plates and transfected with 2µg of ILK promoter reporter vectors with or without 0.2µg of the phRL-TK Renilla Luciferase Reporter Vector. After 24 hours, the transfected cells were exposed to PGE2 and the cells lysed for assessment using the Dual-Luciferase® Reporter Assay System. NSCLC cells were transfected with inactive (ILK-S343A) and superactive ILK (ILK-S343D) cDNA, incubated for 24 hours, treated with or without exogenous PGE2 or with an Sp1 inhibitor for 2 hours. The numbers of viable cells were measured using the CellTiter-Glo® Luminescent Cell Viability Assay. (4026)

Notes: The authors of this review article highlight the use of bioluminescence as a readout for high-throughput ADME/Tox assays. They discuss three strategies for designing bioluminescent assays, using either luciferase, ATP or luciferin substrates as the limiting reagents for a luciferase-catalyzed reaction. Reporter gene assays limit the production of luciferase by tying it to a promoter or DNA regulatory region of interest. Such assays can be used to study genes that are regulated by drugs and other xenobiotics. Bioluminescent assays in which ATP is the limiting reagent of the luciferase reaction can be designed to monitor cell viability or the activity kinases. Bioluminescent assays in which the substrate is limiting can be designed so that the activity of a particular enzyme results in the production of a luciferin substrate that can, in turn, be acted upon by luciferase. (3926)

Notes: The authors designed a high-throughput gene-expression screen to identify compounds that induce a neuroblastoma gene signature in BE(2)-C cells. The screen used Valproic Acid (VPA), an inhibitor of histone deacetylase, as an enhancer. The top hit from the screen was all-trans retinoic acid (ATRA). The authors proposed that ATRA + VPA would reduce cell viability and might induce apoptosis by inducing genes associated with terminal differentiation. They used the CellTiter-Glo® Luminescent Cell Viability Assay in a 96-well format to assess the effects of ATRA and a variety of inhibitors of histone deacetylase on BE(2)-C cell viability. (3931)

Notes: These authors screened a library of 15,000 expression cDNAs in neuroblastoma IMR-32 cells searching for genes that activate the antioxidant response element, ARE. ARE is a cis-acting enhancer element found in the 5´ flanking region of many genes that are involved in protection from oxidative stress. The library was screened using a luciferase reporter construct under the control of an ARE-containing promoter. Luminescence, indicating the presence of cDNA-activating ARE, was measured using the Bright-Glo™ Luciferase Assay System. cDNA clones showing reproducible activation were selected for further analysis. The authors tested the effect of over expression of these ARE activators on the ability to resist oxidative stress. IMR-32 cells expressing the various cDNAs were exposed to hydrogen peroxide or rotenone, and the effect on cell viability was measured using the CellTiter-Glo® Assay. Cells overexpressing the ARE-activators were more resistant to oxidative stress than controls. (3629)

Notes: The authors developed an assay to evaluate antiviral compounds for Epstein-Barr virus (EBV) infections. EBV DNA was isolated using the Wizard® SV 96 Genomic DNA Purification System, and 5µl was used for real-time PCR to quantify the viral DNA. Cytotoxicity of the antiviral compounds was assessed using treated, uninfected Akata cells compared to those with no treatment or infection. After three days when the viral DNA was harvested, cell viability was measured using the CellTiter-Glo® Luminescent Cell Viability Assay. (3761)

Notes: STAT1 is a transcription factor that is involved in a variety of cellular processes and behaves like a tumor suppressor in many ways. It is associated with apoptosis, inhibition of cyclin-dependent kinases, and it may mediate the antitumor effects of IFN-γ. The authors of this study designed a bioluminescent reporter assay to identify small molecules that enhance STAT1-dependent gene expression. The bioluminescent assay was performed in 384-well plates using both stably and transiently transfected cell lines. The screening assay was robust, producing a Z´factor value of 0.92, and it identified three compounds that specifically enhanced STAT1-dependent transcriptional activity. Firefly luciferase activity in stable cell lines was assessed using the Bright-Glo® Luciferase Assay System; luciferase activity in the transiently transfected cells was monitored using the Dual-Luciferase® Assay System. Viability of cells in culture was monitored using the CellTiter-Glo® Assay. (3732)

Notes: This study investigated protein expression profiles in tumors from breast cancer brain metastases. Circulating tumor cells were isolated from a patient with stage IV breast cancer and injected into SCID mice. Tumor cells were then recovered from brain and bone lesions that subsequently developed in these mice. The protein expression profiles of the parent cell line were then compared with those from brain and bone tumors. More than 300 proteins that were up- or down-regulated in the brain tumor cells were identified. Classification of these proteins by function revealed that the majority were associated with cellular metabolism. Sixty-three differentially expressed proteins, including mainly cellular redox-active proteins and proteins involved in glucose and fatty acid oxidation, were selected for further study. Based on the expression data, a metabolic profile of brain metastatic cells was generated. Up-regulation of genes involved in oxidative energy metabolism as indicated by the proteomic analysis was confirmed by quantitative real-time PCR analysis. Consistent with the observation of increased glycolysis and oxidative phosphorylation, the authors also found that levels of cellular ATP were increased in cells from brain metastases. The CellTiter-Glo® Luminescent Cell Viability Assay was used to measure ATP levels in the primary, bone, and brain-derived tumor cells. The authors suggest that adaptation of the tumor cell energy metabolism is a key development in breast cancer brain metastasis. (3613)

Notes: The authors of this paper describe the validation of a bioluminescent assay using the CellTiter-Glo® Reagent to identify novel compounds that inhibit the cytopathic effect of SARS CoV. In this study, three cell viability assay reagents were evaluated: MTS, neutral red, and CellTiter-Glo® Reagent. The CellTiter-Glo®-based assay was chosen because it did not require washing or medium removal; it involved minimal pipetting steps and had a short incubation time, which reduced time in the BSL3 containment facility. The assay was used to screen 100,000 compounds and identified several compounds that inhibited CPE while having a minimal effect on cell viability. (3736)

Notes: NVP-TAE684 was identified as an inhibitor of the constitutive anaplastic lymphoma kinase (ALK) activity associated with the NPM-ALK fusion. NPM-ALK fusion protein is created by translocation event characteristic of anaplastic large-cell lymophomas. NVP-TAE684 was screened against a panel of 35 Ba/F3 cell lines expressing a variety of tyrosine kinases constitutively activated by fusion to TEL. The CellTiter-Glo® Luminescent Cell Viability Assay was used to detect any decrease in viability as a result of treatment with NVP-TAE684. The inhibitory effect of NVP-TAE684 was specific for ALK-associated cell proliferation. In a secondary screen to determine potency, TAE684 was screened against two human anaplastic large-cell lymphoma cell lines. Inhibition of proliferation correlated with dosage and was assessed using the Bright-Glo® Luciferase Assay System. (3738)

Notes: The authors of this study sought to identify inhibitors of myelin-reactive T-cell proliferation. They used spleen cells isolated from transgenic mice expressing T-cell receptors that specifically recognize myelin proteolipid protein residues 139-151 (PLP139-151). Spleen cell suspensions were prepared from the transgenic mice and exposed to PLP in the presence of test compounds. Proliferation was assessed relative to positive and negative controls using the CellTiter-Glo® Luminescent Cell Viability Assay. Of the 41,184 compounds screened, 302 hits were obtained. These 302 compounds were next evaluated for nonspecific cytotoxicity using the CytoTox-ONE™ Homogeneous Membrane Integrity Assay, and compounds causing nonspecific toxicity were eliminated from further consideration. Z´-factor values for the primary screen were robust (> 0.5). (3733)

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